Sources tell CNBC: The Philadelphia company would only make an offer if government approves AT&T-Time Warner deal

Comcast plans a $60 billion cash bid to acquire most assets of 21st Century Fox, but only if AT&T's acquisition of Time Warner gains government approval, CNBC reported Monday night, citing unnamed sources.

The bid by the Philadelphia company would be $8 billion more than Disney's offer of $52 billion.

Comcast also plans to acquire 100 percent of U.K. satellite broadcaster Sky as part of an improved all-cash bid. If Disney gets into a bidding war with Comcast, then Comcast's bid for all of Sky and Fox could get close to $100 billion, these people said.

Comcast is asking investment banks to increase the bridge financing facility they have already arranged for the Sky offer by as much as $60 billion to finance the Fox bid, Reuters previously reported.

Comcast believes Disney cannot match an all-cash bid for Fox because if it adds more stock to a deal, Fox stock will go down, depressing the value of the offer, sources told CNBC.